Signaling is the process of sending signals or signaling information. It is the transfer of special information to control communication. Signaling consists of a protocol or a specialized set of rules that govern the communications of a system. The protocol enables the effective use of the control information (i.e. signals) to provide meaningful communications within a network. Signaling is the mechanism used to operate, control, and manage, the wireless telecommunications network. A good example of a signal is the common ringing alert signal that we are familiar with when someone is calling a telephone. It is distinguished from the user information provided by the telephone network (i.e. voice) since it provides an indication that a party is calling, but it is not the information that is meant to be conveyed by the caller.
Signaling and signaling protocols have become very complex, especially when used to govern telecommunications and the sophisticated services provided today. These advanced signaling protocols provide for the transfer of information among network nodes that enables what is known as intelligent networking. Intelligent networking is a method for providing and interpreting information within a distributed network. A distributed network is structured such that the network resources are distributed throughout the geographic area being served by the network. The network is considered to be intelligent if the service logic and functionality can occur at the distributed nodes in the network. The mobile telecommunications network is distributed and intelligent. Because intelligent networks require such sophisticated signaling, the signaling means has evolved from electrical pulses and tones into very complex messaging protocols. Network signaling is used between network nodes to operate, manage, and control the network to support certain types of functionality.
Signaling information consists of messages that contain parameters that support many functions throughout a network. The primary function required for mobile and cellular-based telecommunications and data networks is mobility and location management. These management functions are key to enabling subscriber mobility in mobile and cellular-based wireless networks. Signaling is provided among mobile switching centers (MSCs), location registers, network gateways and some specialized processing centers to support subscriber mobility within as well as between many different wireless service provider networks.
The primary identifying characteristic of a particular wireless device is the dialable mobile directory number (MDN). The MDN can be up to 15 digits long and is a unique number worldwide among all wireless devices, regardless of country or telecommunications network operator. The format of the MDN has been standardized as the E.164 International Public Telecommunication Number by the International Telecommunications Union, a standards making organization within the United Nations. Because the MDN is unique worldwide to an entity's or individual's mobile service subscription and wireless device, it can be considered an extension of the unique identity of that wireless device's user.
Much of the utility of using an entity's or individual's wireless device as an extension of the identity of the user is enabled by the physical security of wireless devices. Wireless devices are inherently secure due to the properties of digital cellular telecommunications. Digital cellular technology has replaced analog cellular technology worldwide. With this advancement came cellular authentication. Cellular authentication uses a cryptographic security protocol and public key infrastructure that is only made possible by digital communications technology. This cryptographic security protocol prevents a mobile directory number from being used by any wireless device other than the one for which it was originally programmed. The only way to re-use a mobile directory number with another device is by special secure provisioning performed within secure network platforms by the wireless network operator. When this secure provisioning occurs, the mobile director number is securely and solely associated with the device for which it is used. In the case of GSM networks, the secure wireless device is the subscriber identity module, or SIM card, which is associated with an individual and unique mobile service subscription. This is why a SIM card can be used in any GSM-based mobile phone without notifying the wireless network operator. In the case of CDMA networks, the wireless device is the mobile phone itself as SIM cards are not commercially supported today.